1. Field of the Invention
The present invention relates in general to pneumatic therapeutic devices and in particular to a pneumatically-actuated appliance for applying a therapeutic dynamic pressure wave to a human or animal extremity.
2. Description of the Prior Art
In the field of medical treatment, it is known that the application of pressure is helpful in the treatment of edema of the extremities or in the therapeutic prophylaxis for the prevention of deep vein thrombosis. There are two general types of pneumatic appliance systems known in the prior art for such treatment. One system utilizes a single chamber appliance to provide uniform compression of the extremity. The second system, often referred to as a sequential compression system, utilizes an appliance made up of series of chambers or segments. In use, a sequential device inflates these appliance chambers one at a time, starting from the end of the appliance surrounding the most distal portion of the extremity until all of the chambers are inflated. Some inflation devices inflate all of the chambers to a uniform pressure while other devices inflate the most distal chamber to the highest pressure and subsequent chambers to a progressively lower pressure, thereby causing a pressure gradient. In all of the above-described devices, a pneumatic control system is electrically or mechanically operated to provide the desired results.
U.S. Pat. No. 4,030,488 discloses an apparatus for intermittently inflating and deflating a compression sleeve. The sleeve is typical of most prior art sleeves in that it has a plurality of longitudinally-disposed compression chambers which encircle a patient's limb when the sleeve is secured about the limb. The sleeve is inflated in a manner to apply a compressive pressure gradient against the patient's limb which decreases from a lower to an upper portion of the patient's limb to enhance the velocity of blood through the limb. The pressure gradient is achieved by utilizing progressively larger chamber sizes from the lower to the upper limb portions and connecting said chambers to a pressurized fluid source through separate flow control orifices progressively decreasing in effective size corresponding to the progressively located upper chambers.
U.S. Pat. No. 4,206,751 discloses a device for applying compressive pressures to a mammal's limb from a source of pressurized fluid. The device includes a first and a second chamber, with the first chamber being fluid impervious and the second chamber being semi-permeable for virtually continuous ventilation. The device has both the means for connecting the chambers to a source of pressurized fluid and a retaining means positioning and directing the expansion of the chambers onto the limb to provide aid in blood circulating.
U.S. Pat. No. 2,781,041 discloses an apparatus including a sleeve for enclosing a human extremity formed of separate inflatable pressure-applying cells in end-to-end relation and an inner inflatable cell within and embracing the longitudinal extent of the first cells. A source of fluid under pressure is utilized to inflate the first cells successively and then inflate the longer, inner longitudinal cell.